import java.util.Scanner;

public class Two {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n=in.nextInt();
        int[] arr=new int[n];
        for (int i = 0; i < n; i++) {
            arr[i]=in.nextInt();
        }
        int ret=0;
        for (int i = 1; i < n; i++) {
            if (arr[i]>arr[i-1]){
                ret+=arr[i]-arr[i-1];
            }
        }
        System.out.println(ret);
    }


}
